The invention relates to a clamping mechanism and is particularly concerned with the clamping of a vibrator to a reinforcing bar.
In the construction industry, it is frequently necessary to lay a large area of concrete. Such areas can include, for example, foundations for buildings, floors, driveways, columns, walls, ramps, etc.
Concrete is a mixture of cement, sand, and stones, Lime is an ingredient in cement, and water is mixed with the components of the mixture to activate the lime and form a mix or slurry. Concrete exhibits characteristics of strength in compression but is relatively weak in tension.
To increase strength in tension, it is common practice to prepare a grid of reinforcing bars (“rebars”) and then to pour concrete over and around the grid, so that the reinforcing bars improve the tension strength of the poured concrete. After the wet concrete has been poured over and around the grid of reinforcing bars, it is common practice in the art to vibrate the concrete to remove air and voids from the poured mix. In this manner, when the concrete hardens, the slab will be more compact and undesirable pockets within the hardened concrete are avoided, without compromising the integrity of the concrete.
The most common form of concrete vibrator comprises a metal cylinder within which a shaft carrying an eccentric weight is rotatable to cause the metal cylinder to vibrate. The cylinder is mounted on one end of a flexible drive which serves to rotate the shaft and hence vibrate the cylinder. When the vibrating cylinder is introduced into, and immersed in, the wet concrete mix or slurry, vibrations—which may be in the region of 10,000 per minute—agitate the slurry to an extent sufficient to remove air and voids from the slurry.
Another method involves imparting vibrations to the slurry through vibrating the reinforcing bar themselves. Top-mounted vibrators are described in U.S. Pat. No. 6,950,011 and JP 07048927. But these vibrators have certain problems. If a reinforcing bar is too tall—for example, it projects a distance above scaffolding—it is too high for the vibrator operator to reach the top of the bar and the vibrator cannot be mounted for use. A top-mounted vibrator also cannot be used if the end of the reinforcing bar is bent or hooked. Also, if a plurality of reinforcing bars are incorporated in a grid, there may be no individual bars with upwardly projecting ends for mounting in a vibrator.